Hydrosphere (Greek hydro- means "water") in physical geography, describes the collective mass of water that is found under, on and over the surface of a planet.

On Earth, the water cycle is the method of transport for water in the hydrosphere. This includes water under the Earth's surface and in rocks—lithosphere, the water in plants and animals—biosphere, the water covering the surface of the planet in liquid and solid forms, and the water in the atmosphere in the forms of water vapor, clouds, and precipitation.

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See also; Ocean, lake, river, aquifer, glacier, biomass, watershed, water pollution, pedosphere, erosion, Antarctica.